Showing papers by "York University published in 1997"

Sustainable competitive advantage: combining institutional and resource- based views

Abstract: This article suggests that the context and process of resource selection have an important influence on firm heterogeneity and sustainable competitive advantage. It is argued that a firm’s sustainable advantage depends on its ability to manage the institutional context of its resource decisions. A firm’s institutional context includes its internal culture as well as broader influences from the state, society, and interfirm relations that define socially acceptable economic behavior. A process model of firm heterogeneity is proposed that combines the insights of a resource-based view with the institutional perspective from organization theory. Normative rationality, institutional isolating mechanisms, and institutional sources of firm homogeneity are proposed as determinants of rent potential that complement and extend resource-based explanations of firm variation and sustainable competitive advantage. The article suggests that both resource capital and institutional capital are indispensable to sustainable competitive advantage. © 1997 John Wiley & Sons, Ltd.

Prevalence of low femoral bone density in older U.S. adults from NHANES III.

Abstract: Data on the number of U.S. women with low femoral bone mineral density (BMD) are currently available only from indirect estimates. We used dual-energy X-ray absorptiometry (DXA) measurements of femoral BMD from phase 1 of the third National Health and Nutrition Examination Survey (NHANES III, 1988-1991) to estimate prevalences of low femoral BMD in women ages 50 years and older using an approach proposed recently by an expert panel of the World Health Organization (WHO). Cutpoints for low BMD were derived from BMD data of 194 non-Hispanic white (NHW) women aged 20-29 years from the NHANES III dataset. The prevalence of older U.S. women with femoral osteopenia (BMD between 1 standard deviation [SD] and 2.5 SD below the mean of young NHW women) ranged from 34-50% in four different femur regions, which corresponds to approximately 12-17 million women. The prevalence with osteoporosis (BMD > 2.5 SD below the mean of young NHW women) ranged from 17-20%, or approximately 6-7 million women. Prevalences were 1.3-2.4 times higher in NHW women than non-Hispanic black women (NHB), and 0.8-1.2 times higher in NHW versus Mexican American (MA) women. The estimated numbers of NHW, NHB, and MA women with osteopenia were 10-15 million, 800,000-1.2 million, and 300,000-400,000, respectively; corresponding figures for osteoporosis were 5-6 million, 200,000-300,000, and 100,000 respectively. Thus, the first data on BMD from a nationally representative sample of older women show a substantial number with low femoral BMD.(ABSTRACT TRUNCATED AT 250 WORDS)

The Influence of the Management Team's International Experience on the Internationalization Behaviors of SMES

Abstract: Why are some small and medium-sized enterprises (SMEs) more successful in selling outside their domestic markets than are other SMEs in the same industry? Although the traditional explanation is that firms can gain valuable knowledge and resources as they become older and larger, small and young firms are not necessarily disadvantaged if they develop other mechanisms to acquire the requisite knowledge and resources. We examine the role of the management team's international experience as such a mechanism, for the internationalization of Canadian software product firms. We show that internationally experienced management teams have a greater propensity to develop foreign strategic partners and to delay less in obtaining foreign sales after start-up, and that these behaviors are associated with a higher degree of internationalization.

A longitudinal investigation of the relationships between job information sources, applicant perceptions of fit, and work outcomes

Abstract: This longitudinal field study was designed to examine the relationships between job information sources, self-esteem, and perceptions of person-job (P-J) and person-organization (P-O) fit, as well as the relationships between perceptions of fit and work outcomes (job satisfaction, organizational commitment, organizational identification, intentions to quit, stress symptoms, and turnover). The results indicate that the number of formal job information sources and self-esteem were positively related to perceptions of P-J fit, and formal job information sources were positively related to perceptions of P-O fit. Perceptions of P-J fit were positively related to job satisfaction, organizational commitment, organizational identification, and negatively related to stress symptoms and intentions to quit. Perceptions of P-O fit were negatively related to intentions to quit and turnover. In addition, perceptions of fit mediated the relationships between job information sources and self-esteem with job satisfaction, intentions to quit, and turnover. These results highlight the job applicant's perspective of fit, and demonstrate the importance of both P-J and P-O fit perceptions.

The continuity of depression in clinical and nonclinical samples.

Abstract: Historically, depression researchers have examined continuity in terms of whether the symptoms and characteristics of mild, moderate, and severe depression differ in degree along a continuum (i.e., a quantitative difference) or in kind (i.e., qualitative difference). The authors propose a differentiated framework that distinguishes 4 direct tests of continuity (i.e., phenomenological, typological, etiological, and psychometric continuity). They use this framework to suggest that most evidence is consistent with the continuity hypothesis. Moreover, they maintain that the findings of future research can be incorporated into a 2-factor model of depression that allows for both continuities and discontinuities.

Evaluation and intercomparison of global atmospheric transport models using 222Rn and other short-lived tracers

Abstract: Simulations of 222Rn and other short-lived tracers are used to evaluate and intercompare the representations of convective and synoptic processes in 20 global atmospheric transport models. Results show that most established three-dimensional models simulate vertical mixing in the troposphere to within the constraints offered by the observed mean 222Rn concentrations and that subgrid parameterization of convection is essential for this purpose. However, none of the models captures the observed variability of 222Rn concentrations in the upper troposphere, and none reproduces the high 222Rn concentrations measured at 200 hPa over Hawaii. The established three-dimensional models reproduce the frequency and magnitude of high-222Rn episodes observed at Crozet Island in the Indian Ocean, demonstrating that they can resolve the synoptic-scale transport of continental plumes with no significant numerical diffusion. Large differences between models are found in the rates of meridional transport in the upper troposphere (interhemispheric exchange, exchange between tropics and high latitudes). The four two-dimensional models which participated in the intercomparison tend to underestimate the rate of vertical transport from the lower to the upper troposphere but show concentrations of 222Rn in the lower troposphere that are comparable to the zonal mean values in the three-dimensional models.

The seats of reason? An imaging study of deductive and inductive reasoning.

Abstract: WE carried out a neuroimaging study to test the neurophysiological predictions made by different cognitive models of reasoning. Ten normal volunteers performed deductive and inductive reasoning tasks while their regional cerebral blood flow pattern was recorded using [ 15 O]H 2 O PET imaging. In the control condition subjects semantically comprehended sets of three sentences. In the deductive reasoning condition subjects determined whether the third sentence was entailed by the first two sentences. In the inductive reasoning condition subjects reported whether the third sentence was plausible given the first two sentences. The deduction condition resulted in activation of the left inferior frontal gyrus (Brodmann areas 45, 47). The induction condition resulted in activation of a large area comprised of the left medial frontal gyrus, the left cingulate gyrus, and the left superior frontal gyrus (Brodmann areas 8, 9, 24, 32). Induction was distinguished from deduction by the involvement of the medial aspect of the left superior frontal gyrus (Brodmann areas 8, 9). These results are consistent with cognitive models of reasoning that postulate different mechanisms for inductive and deductive reasoning and view deduction as a formal rule-based process.

Dissolved organic and inorganic carbon mass balances in central Ontario lakes.

Abstract: Mass balances of dissolved organic carbon (DOC) and dissolvedinorganic carbon (DIC) based on stream and precipitation inputs andoutflows were measured for seven unproductive lakes in central Ontariobetween 1981 and 1989. Net annual CO2 evasion occurred in sixof the seven study lakes with minor net invasion in the seventh. Atmosphericinvasion might have been significant at certain times of the year, particularlyduring the growing season. Net evasion rates were greater than DIC loadingrates, indicating partial mineralization of the terrestrially-derived DOC in thelakes. A steady state mass balance model adequately described the variationin DOC retention between lakes. Net annual carbon accumulation of forestcommunities based on estimates of net ecosystem production may beoverestimated because of significant export of carbon to lakes via streamsand groundwater, particularly in catchments with extensive peatlands.

The Influence of Institutional and Task Environment Relationships on Organizational Performance: The Canadian Construction Industry

Abstract: This study compared the influence of organizations' relationships to the institutional versus task environment on organizational performance in the Canadian construction industry. This industry is characterized by both intense institutional regulation and strong market competition. Regulatory stringency and resource stringency were proposed as key determinants of the relative importance of institutional versus task environment relations in predicting organizational profitability and productivity. Results favoured the contribution of task environment relations to organizational success in support of an economic or strategic perspective on organizations. However, under highly stringent conditions, institutional relations were shown to be associated significantly with performance, suggesting that future research needs to consider both institutional and task environment effects on organizational performance and success.

The structure of age: in search of barriers to second language acquisition

Abstract: The article examines recent evidence that has been offered to support the notion of a sensitive period for second language acquisition. An analysis of that research leaves several questions unresolved. Two small-scale studies are described which attempt to explore some of these issues. In both cases, it is found that the correspondence between language structures in the first and second language is the most important factor affecting acquisition. The age at which second language acquisitions begins is not a significant factor in either study, but the length of residence, indicating the amount of time spent speaking the second language, is significant in the second study. The conclusion is that there is insufficient evidence to accept the claim that mastery of a second language is determined wholly, or even primarily, by maturational factors. Some suggestions are made for an alternative interpretation based on processing differences between older and younger language learners.

A study of the performance of patients with frontal lobe lesions in a financial planning task.

Abstract: It has long been argued that patients with lesions in the prefrontal cortex have difficulties in decision making and problem solving in real-world, ill-structured situations, particularly problem types involving planning and look-ahead components. Recently, several researchers have questioned our ability to capture and characterize these deficits adequately using just the standard neuropsychological test batteries, and have called for tests that reflect real-world task requirements more accurately. We present data from 10 patients with focal lesions to the prefrontal cortex and 10 normal control subjects engaged in a real-world financial planning task. We also introduce a theoretical framework and methodology developed in the cognitive science literature for quantifying and analysing the complex data generated by problem-solving tasks. Our findings indicate that patient performance is impoverished at a global level but not at the local level. Patients have difficulty in organizing and structuring their problem space. Once they begin problem solving, they have difficulty in allocating adequate effort to each problem-solving phase. Patients also have difficulty dealing with the fact that there are no right or wrong answers nor official termination points in real-world planning problems. They also find it problematic to generate their own feedback. They invariably terminate the session before the details are fleshed out and all the goals satisfied. Finally, patients do not take full advantage of the fact that constraints on real-world problems are negotiable. However, it is not necessary to postulate a 'planning' deficit. It is possible to understand the patients' difficulties in real world planning tasks in terms of the following four accepted deficits: inadequate access to 'structured event complexes', difficulty in generalizing from particulars, failure to shift between 'mental sets', and poor judgment regarding adequacy and completeness of a plan.

Steps toward Determination of the Size and Structure of the Broad-Line Region in Active Galactic Nuclei. IX. Ultraviolet Observations of Fairall 9

Abstract: An 8 month monitoring campaign on the Seyfert 1 galaxy Fairall 9 has been conducted with the International Ultraviolet Explorer in an attempt to obtain reliable estimates of continuum-continuum and continuum-emission-line delays for a high-luminosity active galactic nucleus (AGN). While the results of this campaign are more ambiguous than those of previous monitoring campaigns on lower luminosity sources, we find general agreement with the earlier results: (1) there is no measurable lag between ultraviolet continuum bands, and (2) the measured emission-line time lags are very short. It is especially notable that the Ly? + N V emission-line lag is about 1 order of magnitude smaller than determined from a previous campaign by Clavel, Wamsteker, & Glass (1989) when Fairall 9 was in a more luminous state. In other well-monitored sources, specifically NGC 5548 and NGC 3783, the highest ionization lines are found to respond to continuum variations more rapidly than the lower ionization lines, which suggests a radially ionization-stratified broad-line region. In this case, the results are less certain, since none of the emission-line lags are very well determined. The best-determined emission line lag is Ly? + N V, for which we find that the centroid of the continuum-emission-line cross-correlation function is ?cent ? 14-20 days. We measure a lag ?cent 4 days for He II ?1640; this result is consistent with the ionization-stratification pattern seen in lower luminosity sources, but the relatively large uncertainties in the emission-line lags measured here cannot rule out similar lags for Ly? + N V and He II ?1640 at a high level of significance. We are unable to determine a reliable lag for C IV ?1550, but we note that the profiles of the variable parts of Ly? and C IV ?1550 are not the same, which does not support the hypothesis that the strongest variations in these two lines arise in the same region.

Design and methods of a population-based natural history study of cervical neoplasia in a rural province of Costa Rica: the Guanacaste Project

Abstract: This paper reports on the enrollment phase of a population-based natural history study of cervical neoplasia in Guanacaste, a rural province of Costa Rica with consistently high rates of invasive cervical cancer. The main goals of the study are to investigate the role of human papillomavirus (HPV) infection and its co-factors in the etiology of high-grade cervical neoplasia, and to evaluate new cervical cancer screening technologies. To begin, a random sample of censal segments was selected and enumeration of all resident women 18 years of age and over was conducted with the aid of outreach workers of the Costa Rican Ministry of Health. Of the 10738 women who were eligible to participate, 10049 (93.6%) were interviewed after giving written informed consent. After the interview on cervical cancer risk factors was administered, a pelvic examination was performed on those women who reported previous sexual activity. The pelvic examination included a vaginal pH determination and collection of cervical cells for cytologic diagnosis using three different techniques. Additional cervical cells were collected for determination of the presence and amount of DNA from 16 different types of HPV, and two photographic images of the cervix were taken and interpreted offsite by an expert colposcopist. Finally, blood samples were collected for immunologic and micronutrient assays. Women with any abnormal cytologic diagnosis or a positive Cervigram, as well as a sample of the whole group, were referred for colposcopy, and biopsies were taken when lesions were observed. The enrollment screening will serve as the basis for a prevalent case-control study, and the members of the cohort free from serious disease will be followed actively, at intervals of no more than a year, to study the natural history of HPV infection and the origins of high-grade squamous intraepithelial lesions (HSIL). Details of the field operation are outlined, with particular reference to the realization of this kind of study in developing countries. Descriptive data on the prevalence of disease and exposure to various risk factors are also presented.

A New Self-Report Scale for Assessment of Adolescent Psychopathology: Factor Structure, Reliability, Validity, and Diagnostic Sensitivity

Abstract: This paper describes four studies on self-reported problems in 2,243 adolescent males and females, 12 to 17 years of age. In Study 1, principal-axis factoring of 102 items covering 11 problem domains revealed six factors comprising 49.5% of the variance. Study 2 used confirmatory factor analysis of a 64-item reduced set on a new sample of 408 adolescents. Goodness-of-fit indicators suggested that the six-factor model had excellent fit to the data. Study 3 used data from the 2,157 adolescents used in the first two studies. Coefficient alphas ranged from .83 to .92. Median test-retest reliability for the six factors was .86. There was a consistent structure of the correlation matrix across age and gender. Study 4 was a study of criterion validity, using an additional sample of 86 children with attention-deficit hyperactivity disorder (ADHD). Sensitivity and specificity were high, with an overall diagnostic efficiency of 83%. This new self-report scale, the Conners/Wells Adolescent Self-Report of Symptoms (CASS), may provide a useful component of a multimodal assessment of adolescent psychopathology.

When success breeds failure: the role of self-efficacy in escalating commitment to a losing course of action

Abstract: The search for individual differences relevant to behavior in escalation situations has met with little success. Continuing the search, this study investigated self-efficacy judgments as a potentially important individual difference in escalating commitment to a losing course of action. Predictions derived from self-efficacy theory suggest that self-percepts of high efficacy would exacerbate the economically irrational escalation bias whereas self-percepts of low efficacy would diminish it. These predictions were consistently supported in this laboratory study where business students responded to decision dilemmas in which funds had been committed to a failing course of action. Theoretical and practical implications of these findings are drawn for the escalation and self-efficacy literatures. © 1997 John Wiley & Sons, Ltd.

Women on Corporate Boards of Directors: A Needed Resource

Abstract: This research reports the results of a study of women serving on boards of directors of Canadian private and public sector organizations. These women (N = 278) were an impressive and talented group (eduction, professional designations). In addition, they brought a variety of backgrounds and expertise to their director responsibilities. Most were nominated as a result of recommendations from current board members, CEOs, or someone who knew board members or CEOs. Thus personal relationships (the old boy’s network) as well as track records and appropriate expertise were important factors in board nominations. Women directors thought they had some influence on women’s issues with their boards and board companies. A majority believed that board members should be more diverse, including more women and fewer male CEOs. However they indicated several barriers faced by women in being selected and nominated for board appointments.

Resistance to Bone Resorbing Effects of PTH in Black Women

Abstract: Black women have a lower incidence of vertebral and hip fractures than white women, possibly due to differences in skeletal and mineral metabolism. One suggested mechanism is that blacks have decreased skeletal sensitivity to parathyroid hormone (PTH). To test this hypothesis, we infused h(1–34)PTH in healthy premenopausal black (n = 15) and white (n = 18) women over 24 h and measured serum and urine indices of bone turnover and calcium metabolism throughout the infusion. At baseline, the mean 25-hydroxyvitamin D (25(OH)D) concentration was significantly lower in black women (46%). There were also nearly significant trends toward higher PTH and lower urinary calcium and pyridinoline levels in black women. During infusion, there were no racial differences in the mean (1–34)PTH levels achieved or in resultant elevations of serum calcium or 1,25-dihydroxyvitamin D (1,25(OH)2D) levels. Endogenous parathyroid suppression (measured by (1–84)PTH levels) was also similar between blacks and whites. There was an initial decline in urinary calcium/creatinine in both groups with a greater reduction in black women early in the infusion period (p < 0.05 at 8 h). Furthermore, blacks had lower levels of urinary calcium/creatinine throughout the infusion (p < 0.05 group difference). Bone formation markers (carboxy-terminal propeptide of type I procollagen and osteocalcin) decreased within 8 h and continued to decline throughout the infusion with no distinguishable racial differences (p < 0.05 time trend for both). The most dramatic difference between black and white women in response to PTH infusion was represented by the bone resorption markers. Three separate metabolites of bone resorption (cross-linked N-telopeptide of type I collagen, cross-linked C-telopeptide of type I collagen, and free pyridinoline) all showed substantially greater elevations in white (mean peak increments 399, 725, and 43%) compared with black women (mean peak increments 317, 369, and 17%) during the infusion (p < 0.05 group differences for all three variables). These data strongly suggest that blacks have decreased skeletal sensitivity to the acute resorptive effects of increased PTH. This finding indicates that calcium homeostasis may be accomplished in blacks (during times of relative calcium deficiency) by greater conservation of calcium from nonskeletal sources (most likely renal) with relative preservation of skeletal tissue. These differences in calcium economy could account, at least in part, for the increased bone mass and lower incidence of osteoporotic fractures in black women.

Language Socialization Practices and Cultural Identity: Case Studies of Mexican-Descent Families in California and Texas

Abstract: This article explores the relationship between language and cultural identity as manifested in the language socialization practices of four Mexican-descent families: two in northern California and two in south Texas. The analysis considers both the patterns of meaning suggested by the use of Spanish and English in the speech and literacy performances of four focal children as well as family and dominant societal ideologies concerning the symbolic importance of the two languages, the way language learning occurs, and the role of schooling—all frameworks in which the children's linguistic behaviors were embedded. All four focal children defined themselves in terms of allegiance to their Mexican or Mexican American cultural heritage. However, the families were oriented differently to the Spanish language as a vehicle for affirmation of this commonly articulated group identity. The differences are emblematic of stances taken in a larger cultural and political debate over the terms of Latino participation in U.S. society. Parents in all of the families endorsed Spanish maintenance and spoke of the language as an important aspect of their sense of cultural identity. Only two of the families, however, pursued aggressive home maintenance strategies. Of the other two families, one used a protocol combining some Spanish use in the home with instruction from Spanish-speaking relatives, whereas the family that had moved most fully into the middle class was the least successful in the intergenerational transmission of Spanish, despite a commitment to cultural maintenance.

Normal and neurotic perfectionism in eating disorders: an interactive model.

Abstract: Objective Previous nonclinical research found that both normal (or adaptive) and neurotic (or maladaptive) perfectionism were related, in the positive direction, to attitudes and behaviors associated with eating disorders. However, based on a related body of research, it was hypothesized that these two aspects of perfectionism would relate to body esteem in an interactive rather than an additive fashion. Method: Anorexic and bulimic patients (n = 123) were assessed on multidimensional aspects of perfectionism, neuroticism, and body esteem. Results: Predictions were confirmed. Normal perfectionism was positively associated with body esteem, but only when levels of neurotic perfectionism were low. Conversely, body-image disparagement was most pronounced when normal and neurotic perfectionism were both elevated. Discussion: These findings demonstrate that the interpretation of simple relationships among personality variables—at least in the area of body image and eating disorder research—may provide a misleading picture. © 1997 by John Wiley & Sons, Inc. J Eat Disord 22:421–426 1997.

Convergence across alternative methods for forming strategic groups

Abstract: We studied the convergence of three different methods for identifying group structure (strategic groups) in a single competitive environment. Using a version of the MTMM matrix, we tested the convergent validity of the concept of strategic groups in a mature, geographically delimited competitive environment. We find significant evidence of convergence between competitive structures identified using archival and perceptual data as well as those identified using archival measures of strategy and direct measures of competitors. There is limited evidence of convergence between competitive structures identified from perceptual and direct measures. Taken as a whole, these results are consistent with the emerging theory of strategic groups. We conclude that strategic groups are a theoretical construct and not a methodological artifact, as is suggested by some authors.

“Working model of the child interview”: Infant clinical status related to maternal perceptions

Abstract: Parental perceptions and subjective experience of infants have long been considered important in clinical work with infants and families Using three different samples of infants, we compare mothers' represen- tations of their infants in clinically referred and nonreferred groups, using the Working Model of the Child Inter- view (WMCI) Twenty-four mothers of infants with failure to thrive (and 25 matched controls), 17 mothers of toddlers with sleep disorders (and 20 matched controls), and 13 mothers of infants seen in a general infant psy- chiatry clinic participated Compared to their nonclinical counterparts, mothers of infants with clinical problems had representations of their infants that were significantly more likely to be classified distorted or disengaged Infant gender, age, and birth order were independent of maternal classifications We conclude that the WMCI is a useful structured interview to categorize mothers' perceptions and subjective experience of their infant and re- lationship with the infant Mothers' WMCI classifications are associated with the clinical status of the infant RESUMEN: Las percepciones de la madre y la experiencia subjetiva de los infantes han sido consideradas im- portantes, desde hace tiempo, en cuanto al trabajo clinico con infantes y familias En este estudio, presentamos los resultados de una entrevista clinica acerca de las representaciones que las madres tienen de sus infantes y las comparamos con las representaciones de otras madres de infantes que no pertenecen al mismo grupo Partici- paron veinticuatro madres de infantes con problemas de crecimiento (y sus 25 parejas de control), 17 madres de infants con trastornos para dormir (y sus 20 parejas de control), y 13 madres de infantes que habian sido vistos en una clinica de siquiatria infantil general Comparados con sus contrapartes no clinicas, las madres de infantes

Eating Disorders and Hyperactivity: A Psychobiological Perspective:

Abstract: Objective:To review the eating disorder research investigating the psychobiological connections between self-starvation and high-level exercising, including both animal experimentation and clinical

Gender as Social Practice: Implications for Second Language Acquisition.

Abstract: This paper reviews current research on language and gender and discusses the implications of such work for gender-based research in second language acquisition. Recent work in sociolinguistics, generally, and language and gender research, more specifically, has rejected categorical and fixed notions of social identities in favor of more constructivist and dynamic ones. Thus, in this paper I elaborate a conception of gender that has not generally informed research in the field of second language acquisition, and point to more recent work in the field that theorizes and investigates gender as a construct shaped by historical, cultural, social, and interactional factors.

Inherent variability and the obligatory contour principle

Abstract: English coronal stop deletion is constrained by the preceding segment, so that stops and sibilants favor deletion more than liquids and nonsibilant fricatives. Previous explanations of this constraint (e.g., the sonority hierarchy) have failed to account for the details, but we show that it can be comprehensively treated as a consequence of the obligatory contour principle (OCP). The OCP, introduced to account for a variety of categorical constraints against adjacent identical tones, segments, and so forth, can be generalized as a universal disfavoring of sequences of like features: *[aF] [aFJ. Therefore, coronal stop deletion, which targets the set of segments /t,d/ defined by the features [-son, -cont, +cor], is favored when the preceding segment shares any of these features. But this requires adopting the assumption of inherent variability and interpreting the OCP as a probabilistic constraint with cumulative effects (the more shared features, the greater likelihood of deletion). This suggests an attractive theoretical integration of categorical and variable processes in the grammar. The systematic patterns of variation revealed by sociolinguistic studies of language use are generally modeled in theoretical frameworks that rely on the assumption of "inherent variability" (Labov, 1969; Weinreich, Labov, & Herzog, 1968); that is, the hypothesis that the human language faculty necessarily accommodates and generates variation, and that the workings of grammar have a quantitative, noncategorical, and nondeterministic component. This assumption underlies the variable rule model (Cedergren & Sankoff, 1973; Labov, 1969), which is given a more general formulation as a probabilistic generative model by Sankoff (1978). One of the attractive features of such models is that they offer an integrated account in which social and stylistic dimensions of variation can be modeled along with linguistic dimen. sions. Thus, in a standard variable rule analysis, social differences between individuals in a speech community are represented by their characteristic values of an input parameter, whereas independent linguistic parameters describe favorable and unfavorable linguistic contexts for the occurrence of particular variants. Stylistic variation is another independent parameter, which

Use of Landmark Configuration in Pigeons and Humans: II. Generality Across Search Tasks

Abstract: Pigeons and humans searched for a goal that was hidden in varied locations within a search space. The goal location was fixed relative to an array of identical landmarks. Pigeons searched on the laboratory floor, and humans searched on a table top or an outdoor field. In Experiment 1, the goal was centered in a square array of 4 landmarks. When the spacing between landmarks was increased, humans searched in the middle of the expanded array, whereas pigeons searched in locations that preserved distance and direction to an individual landmark. In Experiment 2, the goal was centered between and a perpendicular distance away from 2 landmarks aligned in the left-fight dimension. When landmark spacing was increased, humans, but not pigeons, shifted their searching away from the landmarks along the perpendicular axis. These results parallel those obtained in touch-screen tasks. Thus, pigeons and humans differ in how they use landmark configuration.